/**
 * @desc 兼容不同的浏览器居中scrollCenter
 * @author ZhangHuihua@msn.com
 */
(function($){
    $.fn.extend({

        getWindowSize: function(){
            if ($.browser.opera) { return { width: window.innerWidth, height: window.innerHeight }; }
            return { width: $(window).width(), height: $(window).height() };
        },
        /**
         * @param options
         */        
        scrollCenter: function(options){
            // 扩展参数
            var op = $.extend({ z: 1000000, mode:"WH"}, options);
            
            // 追加到 document.body 并设置其样式
            var windowSize = this.getWindowSize();

            return this.each(function(){
                var $this = $(this).css({
                    'position': 'absolute',
                    'z-index': op.z
                });
                
                // 当前位置参数
                var bodyScrollTop = $(document).scrollTop();
                var bodyScrollLeft = $(document).scrollLeft();
                var movedivTop = (windowSize.height - $this.height()) / 2 + bodyScrollTop;
                var movedivLeft = (windowSize.width - $this.width()) / 2 + bodyScrollLeft;
                
                if (op.mode == "W") {
                    $this.appendTo(document.body).css({
                        'left': movedivLeft + 'px'
                    });
                } else if (op.model == "H"){
                    $this.appendTo(document.body).css({
                        'top': movedivTop + 'px'
                    });    
                } else {
                    $this.appendTo(document.body).css({
                        'top': (windowSize.height - $this.height()) / 2 + $(window).scrollTop() + 'px',
                        'left': movedivLeft + 'px'
                    });
                }
                
                // 滚动事件
                $(window).scroll(function(e){
                    var windowSize = $this.getWindowSize();
                    var tmpBodyScrollTop = $(document).scrollTop();
                    var tmpBodyScrollLeft = $(document).scrollLeft();
                    
                    movedivTop += tmpBodyScrollTop - bodyScrollTop;
                    movedivLeft += tmpBodyScrollLeft - bodyScrollLeft;
                    bodyScrollTop = tmpBodyScrollTop;
                    bodyScrollLeft = tmpBodyScrollLeft;

                    // 以动画方式进行移动
                    if (op.mode == "W") {
                        $this.stop().animate({
                            'left': movedivLeft + 'px'
                        });
                    } else if (op.mode == "H") {
                        $this.stop().animate({
                            'top': movedivTop + 'px'
                        });
                    } else {
                        $this.stop().animate({
                            'top': movedivTop + 'px',
                            'left': movedivLeft + 'px'
                        });
                    }
                    
                });
                
                // 窗口大小重设事件
                $(window).resize(function(){
                    var windowSize = $this.getWindowSize();
                    movedivTop = (windowSize.height - $this.height()) / 2 + $(document).scrollTop();
                    movedivLeft = (windowSize.width - $this.width()) / 2 + $(document).scrollLeft();
                    
                    if (op.mode == "W") {
                        $this.stop().animate({
                            'left': movedivLeft + 'px'
                        });
                    } else if (op.mode == "H") {
                        $this.stop().animate({
                            'top': movedivTop + 'px'
                        });
                    } else {
                        $this.stop().animate({
                            'top': movedivTop + 'px',
                            'left': movedivLeft + 'px'
                        });
                    }
                    
                });
            });
            
        }
    });
})(jQuery);